1. Technical Field
The present disclosure relates to a circuit device, an oscillator, an electronic apparatus, a moving object, and so on.
2. Related Art
In the past, there has been known a temperature compensated oscillator called a temperature compensated crystal oscillator (TCXO). The TCXO can be used as a reference signal source or the like in, for example, a portable communication terminal, GPS-related equipment, wearable equipment, or in-car equipment.
The TCXO can include an ATCXO standing for an analog-type temperature compensated oscillator, and a DTCXO standing for a digital-type temperature compensated oscillator. As the related art of the ATCXO, there is known a technology disclosed in JP-A-2012-199631. As the related art of the DTCXO, there is known a technology disclosed in JP-A-64-82809.
The digital-type oscillator such as a DTCXO has an advantageous aspect in the reduction of power consumption compared to the analog-type oscillator such as an ATCXO. For example, in the ATCXO, a lot of consumption current flows in an analog current of the circuit device. In particular in the ATCXO, the power consumption dramatically increases if it is attempted to increase the order of the approximation function in the temperature compensation circuit (an approximation function generation circuit) as an analog circuit in order to improve the frequency accuracy, or to decrease the noise by increasing the current flowing through the transistors of the analog circuit. Therefore, there is a problem that it is difficult to realize both the improvement in frequency accuracy and the reduction of power consumption at the same time.
On the other hand, in the digital-type oscillator such as a DTCXO, it has been revealed that if a frequency drift of an oscillation frequency due to a temperature change exceeds, for example, an allowable frequency drift range, a variety of failures occur in a device using the oscillation signal of the oscillator.
Further, it has also been revealed that due to the variation of the oscillation frequency, there occurs a noise (spurious) with an intention corresponding to the variation to degrade the C/N characteristic (a carrier-to-noise ratio, a CN ratio) of the circuit device. Due to the degradation of the C/N characteristic, the accuracy of the data obtained based on the signal from the oscillator such as a DTCXO degrades.